Tamoxifen and related compounds decrease membrane fluidity in ox-brain phospholipid liposomes: their order of effectiveness is, 4-hydroxytamoxifen > 17β-oestradiol > tamoxifen >cis-tamoxifen >N-desmethyltamoxifen > cholesterol. A good positive correlation was demonstrated between the decrease in membrane fluidity by these compounds and their antioxidant ability as inhibitors of liposomal and microsomal lipid peroxidation (correlation coefficient, r = 0.99, P < 0.001, in both cases). The ability of tamoxifen to decrease membrane fluidity is suggested to be the mechanism of its antioxidant action and is discussed in relation to its anticancer and cardioprotective actions.
